Heating element for a cooking appliance

ABSTRACT

A heating element for a cooking appliance includes terminals that act as electrically conductive contact points. One or more buses are arranged between the terminals, and connect one or more heating element segments in a zig-zag configuration. The heating element segments are connected in series and are arranged parallel with one another. Each heating element segment includes a plurality of cutouts linked together and having an elliptical shape. The terminals, heating element segments, and buses are a continuous single sheet of conductive material. A method of making the heating element includes forming a pattern into the sheet of conductive material by etching the pattern into the conductive sheet using photolithography.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/443,548 filed Jan. 6, 2017, and U.S. Provisional PatentApplication No. 62/524,583 filed Jun. 25, 2017, the disclosures of whichare hereby incorporated by reference in their entirety.

BACKGROUND

Various appliances are available for heating and cooking food. An oven,for example, is often used for cooking food at lower to moderatetemperatures for fairly long periods of time. A microwave oven, on theother hand, utilizes microwave energy and can heat and cook food morerapidly, but the quality of food cooked in a microwave is oftenundesirable. Toasters and toaster ovens similarly suffer from certaindrawbacks, such as slow cooking times and/or poor cooked food quality.Therefore, there is a need for improved cooking appliances that overcomethe drawbacks of the prior art.

SUMMARY

In general terms, this disclosure is directed to a heating element for acooking appliance. In some embodiments, and by non-limiting example, theheating element includes a plurality of conductive strips that generateinfrared radiation. The infrared radiation provides faster cooking timesand results in improved cooked food quality.

In one aspect, the disclosed technology relates to a heating element fora cooking appliance, the heating element comprising: first and secondterminals; and one or more heating element segments extending betweenthe first and second terminals, each heating element segment having aplurality of cutouts arranged in a repeating pattern, each cutout havingan elliptical shape. The first and second terminals and the one or moreheating element segments are a continuous single sheet of material.

In one example, the heating element includes one or more buses arrangedbetween the first and second terminals, the one or more buses connectingthe one or more heating element segments in a zig-zag configuration. Inanother example, the heating element includes a first set of heatingelement segments having a first length, a second set of heating elementsegments having a second length, and a third set of heating elementsegments having a third length. In some examples, the third set ofheating element segments are arranged between the first and second setsof heating element segments, and the first length is less than thesecond length, and the second length is less than the third length. Insome examples, the length of the first set of heating elements is about70% to about 90% the length of the third set of heating elements, andthe length of the second set of heating elements is about 80% to about99% the length of the third set of heating elements. In some examples,the first length, second length, and third length define an optimizedheating surface area that reduces energy waste.

In one aspect, the one or more heating element segments are connected inseries and are arranged parallel to each other. In another aspect, theheating element has a total width greater than a sum of widths of theone or more heating element segments. In some examples, the total widthof the heating element is about 35% to about 45% greater than the sum ofwidths of the one or more heating element segments.

In some examples, each cutout is defined by first and second walls thatare curved and that flare out in opposing directions along a verticalaxis. In some examples, each cutout is adjacent to an opposing first orsecond wall of an adjacent cutout.

In one aspect, the heating element generates infrared radiation when avoltage is applied across the heating element. In one aspect, theheating element is included in a toaster.

In another aspect, the disclosed technology relates to a cookingappliance comprising: a housing defining at least one cooking cavity forreceiving food therein; an electrical power cable including electricalconductors, configured for connection to a mains power source; and aheating assembly arranged to provide infrared radiation into the cookingcavity, the heating assembly being directly electrically connected tothe electrical conductors of the electrical power cable, the heatingassembly including at least one heating element that includes: first andsecond terminals; and one or more heating element segments extendingbetween the first and second terminals, each heating element segmentincludes a plurality of cutouts linked together, each cutout having anelliptical shape; wherein the first and second terminals and the one ormore heating element segments are a continuous single sheet of material.

In some examples, the at least one heating element further includes oneor more buses arranged between the first and second terminals, the oneor more buses connecting the one or more heating element segments in azig-zag configuration. In one aspect, the at least one heating elementincludes a first set of heating elements having a first length, a secondset of heating element segments having a second length, and a third setof heating element segments having a third length; the third set ofheating element segments are arranged between the first and second setsof heating element segments, and wherein first length is less than thesecond length, and the second length is less than the third length. Insome examples, the first length, second length, and third length definean optimized heating surface area that reduces energy waste by limitingheat from being applied to spaces in the at least one cooking cavitythat are not proximate to food.

In some examples, each cutout in the at least one heating element isdefined by first and second walls that are curved and that flare out inopposing directions along a vertical axis.

In one aspect, the cooking appliance is a toaster having parallelcooking cavities; and wherein heating elements are mounted adjacent toopposing sides in each cooking cavity.

In another aspect, the disclosed technology relates to a method ofmaking a heating element, the method comprising: obtaining a singlesheet of conductive material; and forming a pattern into the sheet ofconductive material; wherein the pattern defines one or more heatingelement segments connected together in series and extending betweenfirst and second terminals, each heating element segment includes aplurality of cutouts linked together, each cutout having an ellipticalshape; and wherein each heating element segment includes a plurality ofelliptically shaped cutouts spaced apart from one another in a chainedor linked pattern.

In some examples, the step of forming a pattern comprises etching thepattern into the conductive sheet using photolithography.

A variety of additional aspects will be set forth in the descriptionthat follows. The aspects can relate to individual features and tocombination of features. It is to be understood that both the foregoinggeneral description and the following detailed description are exemplaryand explanatory only and are not restrictive of the broad inventiveconcepts upon which the embodiments disclosed herein are based.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of an example cooking appliance.

FIG. 2 is a schematic block diagram of the example cooking appliance.

FIG. 3 is a schematic diagram illustrating an example heating assembly.

FIG. 4 is a schematic diagram illustrating another example heatingassembly.

FIG. 5 is a schematic diagram illustrating an example of a heatingelement.

FIG. 6 is a front plan view of another example heating element.

FIG. 7 is an isometric view of the example heating element shown in FIG.5.

FIG. 8 is a front plan view of a reflector positioned behind the exampleheating element shown in FIG. 5.

FIG. 9 is a side sectional view of a cooking appliance that includes theexample heating element shown in FIG. 5.

FIG. 10 is a front sectional view of a cooking appliance that includesthe example heating element shown in FIG. 5.

FIG. 11 is an enlarged view of the example heating element shown in FIG.5.

FIG. 12 is another enlarged view of the example heating element shown inFIG. 5.

DETAILED DESCRIPTION

Various embodiments will be described in detail with reference to thedrawings, wherein like reference numerals represent like parts andassemblies throughout the several views. Reference to variousembodiments does not limit the scope of the claims attached hereto.Additionally, any examples set forth in this specification are notintended to be limiting and merely set forth some of the many possibleembodiments for the appended claims.

FIG. 1 is an isometric view of an example cooking appliance 100. Thecooking appliance 100 includes a housing 102 that defines one or morecooking cavities 104. In use, food is placed within one of the cookingcavities 104 where it is heated by the cooking appliance 100. Thecooking appliance 100 operates to supply energy to food arranged withinthe one or more cooking cavities 104. The cooking appliance 100 can takea variety of forms, such as a toaster, a toaster oven (including, forexample, a pizza oven), a microwave oven, an electric grill, a contactcooker (including, for example, a contact grill or griddle), or a slowcooker.

FIG. 2 is a schematic block diagram of the cooking appliance 100 thatincludes a housing 102, a cooking cavity 104, a heating assembly 106including at least one heating element 108, an electrical control andcoupling 110, and a power cable 112. In certain examples, the electricalcoupling and control 110 includes electrical conductors 114 (includingconductors 114A and 114B) and a coupler 116. In some examples, the powercable 112 includes electrical conductors 112A and 112B and a plug 118.The cooking appliance 100 is powered by a power source, for example, byconnecting the power cable 112 to a mains power source 90.

The cooking appliance 100 includes a heating assembly 106, whichincludes one or more heating elements 108. The heating elements 108 areelectrically coupled to the power cable 112, such as through anelectrical control and coupling 110, and can be electrically connectedto a power source such as the mains power source 90. Examples of theheating assembly 106 are illustrated and described in further detailwith reference to FIGS. 3 and 4.

In at least some examples, each heating element 108 is formed of aplurality of conductive strips. When powered, electricity flows throughthe heating element 108 generating heat. As the temperature of theheating element rises, the heating element 108 begins to generateinfrared radiation. The heating element 108 continues to generateinfrared radiation until the heating assembly is disconnected from thepower source. The infrared radiation is directed to the cooking cavity104 where it operates to heat food in the cooking cavity. Examples ofthe heating element 108 are illustrated and described in further detailwith reference to FIGS. 3-5.

Certain examples include an electrical control and coupling 110 whichincludes conductors 114 and coupling 116. In some examples, the coupling116 includes a switch or other control device for selectively couplingthe heating assembly 106 to the power source 90 to turn on and off theheating assembly 106. In some examples, when the electrical control andcoupling 110 has selectively coupled the heating assembly 106 to thepower source 90, the heating assembly 106 is directly coupled to thepower source through the conductors 114A and 114B and the conductors112A and 112B of the power cable 112. In such examples, the cookingappliance 100 does not require a separate power supply including avoltage transformer or other power regulation electronics to supply theelectricity from the mains power source 90 to the heatingassembly—instead the electricity can be supplied directly through theconductors.

FIGS. 3 and 4 are schematic diagrams illustrating examples of theheating assembly 106. In the example shown in FIG. 3, the exampleheating assembly 106 includes three heating elements 108A, 108B, and108C. The heating assembly 106 is selectively coupled to a power source,such as by a switch. The switch can be manually controlled by a user(e.g., by pressing down on a toaster, or by depressing a power button),or can be controlled by an electronic control system such as in amicrowave oven. When coupled to the power source, the heating assembly106 is energized. When directly coupled to a mains power source, theheating assembly 106 is energized by an alternating current signal. InNorth America, the alternating current signal typically has a voltage of+/−120 V and a frequency of 60 hertz. In other parts of the world, othersignals (such as having different voltages) are used and the heatingassembly 106 can be designed to work with any appropriate mains powersource, or even a DC power source such as from a battery or utilizing apower inverter. In the example discussed herein, a voltage of +/−120 Vis discussed for illustrative purposes.

In this example, the heating assembly 106 includes three heatingelements 108A, 108B, and 108C arranged in series. The heating element108A is connected at one end to the AC line of the mains power source,and is connected at the other end to an end of the heating element 108B.The ends of the heating element 108B are connected to ends of theheating elements 108A and 108C. One end of the heating element 108C isconnected to the end of the heating element 108B and the other end ofthe heating element 108C is connected to the neutral line of the mainspower source.

In this configuration, the heating elements 108A, 108B, and 108C act asa voltage divider to divide the +/−120 V signal across the threeelements. In other words, each heating element sees a voltage across itof VAC/3 elements=VAC/3 or about 40 V.

In order to obtain a desired power output from each element 108, theheating elements 108 can be designed to have a desired resistance. Forexample, to obtain a power output of 500 watts from each element (1500 Wtotal from three elements), the desired resistance is calculated byP=I*V, or 500 W=I*40 V. Therefore, the desired current is I=500 W/40V=12.5 Amps. The resistance is then computed using V=I*R, or R=V/I=40V/12.5 Amps=3.2 Ohms. The calculations can be adjusted to obtain otherpower outputs. These values can be used in the design of the heatingelements as discussed in further detail herein.

In the example shown in FIG. 4, the example heating assembly 106includes four heating elements 108A, 108B, 108C, and 108D. As in theexample shown in FIG. 3, the heating elements 108 are arranged inseries. Because there are now four heating elements, the mains voltageis now divided across four elements, resulting in a lower voltage acrosseach element, e.g., 30 V. Therefore, in this example it may be desirableto adjust the particular configuration of the heating element in view ofthe decreased voltage.

The heating assembly 106 can have one or more heating elements,including for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more. One benefitof having multiple heating elements is that the heating elements may bepositioned in different locations within the cooking appliance 100. Forexample, in a toaster there may be one heating element positioned oneach side of the cooking cavities so as to heat a slice of bread on eachside. In a multi-slice toaster, additional heating elements can be usedfor each cooking cavity. As another example, a toaster oven or microwavecan have heating elements arranged on the top and bottom of the cookingcavity such that radiative heating may be combined with one or moreadditional mechanisms such as free/forced convection and microwave.Other embodiments are also possible having various numbers of heatingelements arranged in various possible configurations.

FIG. 5 is a schematic diagram illustrating an example of a heatingelement 108. In this example diagram, the heating element 108 includesterminals 130 (including 130A and 130B), heating element segments 134(including 134A, 134B, 134C, and 134D), and buses 136 (including 136A,136B, and 136C). In accordance with the present disclosure, the heatingelement 108 can include one or more heating element segments 134, andtypically includes at least a plurality of heating element segments 134.The example shown in FIG. 5 illustrates four heating element segments134, but also includes an ellipsis representing the fact thatembodiments can have more or fewer heating element segments 134.

The heating element 108 includes terminals 130A and 130B arranged ateach end. The terminals 130 are electrically conductive contact pointsto which the heating element 108 can be connected to a power source orother heating elements 108 (such as shown and described with referenceto FIGS. 3 and 4). In this example the terminals 130A and 130B are alsoeach connected to at least one heating element segment 134 of theheating element 108. For example, terminal 130A is connected at one endof heating element segment 134A and terminal 130B is connected at oneend of heating element segment 134D.

The heating element segments 134 are the parts of the heating element108 that heat up and generate infrared radiation when electricity ispassed through them. In some embodiments the heating element segments134 are formed of a conductive material. In one example, the conductivematerial is an alloy of at least nickel and chromium, also known asNichrome.

The buses 136 are arranged to connect the heating element segments 134in series. The buses 136 are electrically conductive strips that areconnected at ends of adjacent heating element segments 134 and act tomechanically support the heating element segments 134, and also toconduct electricity between the adjacent heating element segments 134.In this example, bus 136A is connected to ends of heating elementsegments 134A and 134B; bus 136B is connected to ends of heating elementsegments 134B and 134C; and bus 136C is connected to ends of heatingelement segments 134C and 134D. In some embodiments as shown in FIG. 5,the heating element 108 has a zig-zag shape in which the heating elementsegments 134 and buses form a zig-zag shape that follows one heatingelement segment 134A to a bus 136A, which is then connected to anotherheating element segment 134B and a bus 136B, etc.

When energized, a voltage is applied across the terminals 130A and 130B,such as shown in FIGS. 3 and 4. When the heating element segments 134are arranged in series as shown in FIG. 5, the heating element segments134 act as a voltage divider to divide the total voltage applied acrossthe heating element 108. When the heating element segments 134 have thesame size and electrical characteristics, the voltage is evenly dividedacross each element. Therefore, if 40 V is applied to terminals 130A and130B, and there are a total of four heating element segments 134, eachheating element segment 134 has a voltage applied across it of the 10 V.If additional heating element segments 134 are present, the voltage isfurther divided.

With a given voltage being applied across a heating element segment, anda selected conductive strip material, the heating element segments canbe designed to have a desired level of power output by adjusting thelength L to width W ratio of the heating element. In order to decreasethe power output (by decreasing the current flow), the ratio isincreased so that the strip is longer and/or narrower. In order toincrease the power output (by increasing the current flow), the ratio isdecreased so that the strip is shorter and/or wider.

An advantage of some examples is that the heating assembly 106 canoperate directly from the power supplied by the mains power source 90(FIG. 2), without requiring complex and costly electronics to modify thepower. For example, in some embodiments the heating assembly does notrequire a transformer or other voltage rectifier or inverter electroniccircuitry in order to transform the power from an original form intoanother form suitable for the heating assembly 106. Instead, the heatingassembly 106 can, in some embodiments, operate directly from the powersupplied by the mains power source 90.

Referring now to FIGS. 6 and 7, an example heating element 150 includesterminals 130 (including terminals 130A and 130B), heating elementsegments 134 (including segments 134A-F), and buses 136 (including buses136A-E). In the example depicted in FIGS. 6 and 7, the heating element150 includes six heating element segments 134A-134F connected togetherby five buses 136A-136E, but in other examples the heating element 150may include more or fewer heating element segments 134. Other examplesmay include a quantity of heating element segments 134 that range fromabout 1 to about 20, or from about 2 to about 12. Some examples may havean even number of heating element segments 134 such as 2, 4, 6, 8, 10,or 12 etc.

The heating element 150 has a total width W2 and each heating elementsegment 134 has a width W1. The total width W2 is greater than the sumof the widths W1 of each heating element segment 134 in the heatingelement 150. In certain examples, the total width W2 of the heatingelement is about 35% to about 45% greater than the sum of the widths W1of the one or more heating element segments. In certain examples, thetotal width W2 of the heating element 150 is in a range from about 2inches to about 18 inches, or in a range from about 3 inches to about 12inches, or in a range from about 4 inches to about 6 inches.

The heating element 150 includes terminals 130A and 130B arranged atopposite ends of the heating element 150. The terminals 130 areelectrically conductive contact points that connect the heating element150 to a power source or other heating elements (such as shown anddescribed with reference to FIGS. 3 and 4). In this example, theterminals 130A and 130B are also each connected to at least one heatingelement segment 134 of the heating element 150. For example, terminal130A is connected at one end of heating element segment 134A andterminal 130B is connected at one end of heating element segment 134F.

The heating element segments 134 may be connected in series so that thecurrent path between the terminals 130A, 130B is increased as comparedto a surface area having only a single heating element segment 134. Forexample, the current path is at least six times the length L1 of thefirst heating element segment 134A. By increasing the current pathbetween the terminals 130A, 130B, higher voltages may be employed by thepower source (e.g., 110V that may be the same as the voltage source towhich the appliance is plugged into) and/or lower current, which may behelpful in avoiding use of a power converter or otherwise reduce thecost of components of an appliance that includes the heating element150.

In the example shown in FIGS. 6 and 7, the heating element 150 has atotal length L0 and a first set of outermost heating element segments(e.g., segments 134A and 134F) have a first length L1, a second set ofinner heating element segments (e.g., segments 134B and 134E) have asecond length L2, and a third set of innermost heating element segments(e.g., segments 134C and 134D) have a third length L3. In the exampledepicted in FIGS. 6 and 7, three sets of heating element segments aredepicted, and each set includes two heating element segments. In otherexamples, a set of heating element segments may include a single heatingelement segment or may include more than two heating element segments,and the heating element 150 may include more than or fewer than threesets of heating element segments.

The length of each heating element segment 134 (e.g., L1, L2, or L3) isgreater than the width W1 of each heating element segment 134. The ratioof the lengths L1, L2, L3 to the width W1 can be selected in order toobtain a desired power output, current flow, and resistance. In someexamples, the heating element segments 134 each have a width W1 in arange from about 0.1 inches to about 6 inches, or in a range from about¼ inch to about 1 inch. In some examples, the width W1 is about ½ inch.In some examples, the lengths L1-L3 of the heating element segments 134may range from about 2 inches to about 12 inches, or may range fromabout 3 inches to about 8 inches. In certain examples, the length L1 ofthe first set of heating elements is about 70% to about 90% the lengthL3 of the third set of heating elements. In certain examples, the lengthL2 of the second set of heating elements is about 80% to about 99% thelength L3 of the third set of heating elements.

In the example heating element 150 depicted in FIGS. 6 and 7, the bus136A which connects heating element segments 134A and 134B has an elbowor bent shape for accommodating the different lengths L1, L2 betweenthese heating element segments. The bus 136E which connects heatingelement segments 134E and 134F also has an elbow or bent shape foraccommodating the different lengths L1, L2 between these heating elementsegments. Buses 136B, 136C, and 136D each have a straight or linearshape for connecting adjacent heating element segments (e.g., heatingelement segments 134B and 134C, heating element segments 134C and 134D,and heating element segments 134D and 134E). In certain examples, theshapes of the terminals 130 (e.g., terminals 130A-B) and the buses 136(e.g., buses 136A-E) may vary.

The buses 136A-E and the terminals 130A, 130B each include one or moreapertures 144 to provide mechanical contact points. In certain examples,electrically insulated mechanical supports are fastened to the apertures144 to hold the terminals 130 and buses 136 in a desired position withrespect to a cooking cavity of an appliance such as the cookingappliance 100. In some examples, the mechanical supports may includesprings to support the heating element 150, which allows the heatingelement to expand and contract as it heats up and cools down.

During operation, electricity is supplied to the heating element 150 byelectrically connecting the terminals 130A and 130B to the power source.As electricity flows through the heating element 150, the material ofthe heating element segments 134 begins to heat up and glow. Typicallythe glowing begins at temperatures between about 500 and 550 degrees C.(about 1,000 degrees F.). When the heating element segments 134 glow,they generate and radiate infrared radiation. In some embodiments theheating element segments 134 have a temperature in a range from about800 to about 900° C. during operation, or about 850° C.

Referring now to FIGS. 8-10, a reflector 146 may be positioned adjacentthe heating element 150 when the heating element 150 is mounted inside acooking appliance. In certain examples, rivets may be fastened throughthe apertures 144 for attaching the heating element 150 to the reflector146 proximate to a cooking cavity 104 of the cooking appliance 100.

In the example depicted in FIG. 9, the cooking appliance 100 is atoaster having a slice of bread partially inserted in a cooking cavity104 (e.g., bread slot). FIG. 10 depicts a front cross-sectional view ofthe cooking appliance 100 as having two cooking cavities 104 (e.g.,bread slots), and a reflector 146 and heating element 150 are positionedon opposing sides in each cooking cavity 104. Accordingly, in theexample of FIGS. 9 and 10, the cooking appliance 100 includes fourreflectors 146 and four heating elements 150. Although the cookingappliance 100 in FIGS. 9 and 10 is depicted as a toaster having twocooking cavities 104 (e.g., bread slots), it is contemplated that theheating element 150 may be used in different types of cooking appliancesincluding toaster ovens, pizza ovens, microwave ovens, electric grills,contact cookers (including, for example, contact grills or griddles), orslow cookers. Also, it is contemplated that the heating element 150 maybe used in toasters having more than or fewer than two bread slots.

During operation of the heating element 150, the heating elementsegments 134 radiate infrared radiation in all directions. The reflector146 reflects the heat generated by the heating element segments 134 backtoward the heating element 150 and a cooking cavity 104 of the appliance100 (such as a bread slot in a toaster cooking appliance). The reflectedinfrared radiation further helps to heat the heating element segments134 allowing them to heat up more quickly and to generate additionalinfrared radiation. Additionally, the reflector 146 provides boththermal and electrical insulation in the cooking appliance 100 such thatthe heat and current of the heating element 150 does not transmit to thehousing 102 of the cooking appliance 100.

The reflector 146 may include several tabs 148 along the top, bottom,and sides that anchor the reflector 146 inside the chassis of thecooking appliance 100. Additionally, each tab 148 may include anaperture 152 that can receive a fastener for securing the reflector 146to the housing 102 of the cooking appliance 100. In FIG. 8, thereflector 146 is depicted as having a length L4 and a width W4. Incertain examples, the length L4 may be about 5.5 to about 6.5 inches,and the width W4 may be about 4.5 to about 5.5 inches. The reflector 146can be made from a sheet of dielectric material such as Phlogopite hightemperature mica or similar materials. In certain examples, thereflector 146 may have a thickness of about 0.015 to about 0.045 inches.

Referring now to FIGS. 8-10, the arrangement of the heating elementsegments 134A-134F provides an optimized heating surface area HS_(A)adjacent the reflector 146. The optimized heating surface area HS_(A) isdefined by the lengths L1-L3 of the heating element segments 134A-134F.In certain examples, the optimized heating surface area HS_(A) may matchthe shape of a typical piece of toast having a square or rectangularbottom and a rounded top. When used in a toaster cooking appliance,heating elements 150 may be positioned on each side of a cooking cavity104 for toasting the sides of a slice of toast. The optimized heatingsurface area HS_(A) of the heating element 150 reduces energy waste bylimiting heat from being applied to spaces in the cooking cavity 104that are not proximate to a food item such as a slice of toast.

Referring now to FIG. 11, an enlarged view of the heating element 150 isdepicted showing the heating element segment 134B extending between thebus 136A and the bus 136B. Each heating element segment 134A-F has arepeating pattern 154 formed from a plurality of cutouts 140. Thecutouts 140 are spaced apart from one another in the repeating pattern154, and are surround by rounded corners. In some examples, therepeating pattern 154 is formed of two columns of cutouts 140 and anested third column of cutouts 140 that overlaps and/or is arrangedbetween the first two columns of cutouts 140. The repeating pattern 154may allow the heating element 150 to provide a uniform radiant heating.

Referring now to FIG. 12, the cutouts 140 have an elliptical shape suchthat they are substantially oval or circular. For example, each cutout140 includes first and second walls 140 a, 140 b that are curved andthat flare out in opposing directions along a vertical axis A-A. In thismanner, each cutout 140 is separated along the vertical axis A-A fromanother cutout 140. Additionally, each cutout 140 is linked to anopposing wall 140 a, 140 b of an adjacent cutout 140. Each cutout 140 issymmetrical about both the vertical axis A-A and the horizontal axisB-B.

The curved shape of the cutouts 140 increases the current path betweenthe terminals 130A, 130B of the heating element 150 so that highervoltages may be employed and/or a lower current may be used to heat theheating element 150. Additionally, the shape of the cutouts 140 providesa complex resistance path that may help reduce hot spots in the heatingelement 150.

As depicted in FIG. 12, the cutouts 140 may each have an individualwidth W5 and an individual length L5. In certain examples, the width W5may range from about 0.20 inches to about 0.35 inches, and the length L5may range from about 0.06 inches to about 0.16 inches.

In certain examples, the heating element 150 is a single sheet ofmaterial such that the terminals 130 (including terminals 130A and130B), heating element segments 134 (including segments 134A-F), andbuses 136 (including buses 136A-E) are all continuous with one another.Accordingly, separate elements or pieces are not used for connecting theterminals 130, heating element segments 134, and buses 136 since theyare all part of the same continuous sheet of material. In certainexamples, the heating element 150 is a single sheet ofIron-Chrome-Aluminum alloy or similar alloy material. In other examples,the heating element 150 is a single sheet of an alloy of at least nickeland chromium, known as Nichrome.

To form the terminals 130, heating element segments 134, and buses 136as a single piece of material, a blank sheet is cut from a roll ofmaterial and is then processed. In certain examples, the blank sheet isprocessed using photolithography to remove unwanted portions of thesheet through an etching process, leaving only the desired features ofthe heating element 150. In certain examples, the photolithographyprocess includes the steps of applying a photoresist material onto asurface of the blank sheet, aligning a photomask having an inversepattern to that of the desired heating element 150 with the sheet andthe photoresist, exposing the photoresist to ultraviolet light throughthe photomask, and removing the portions of the photoresist exposed toultraviolet light. Etching is then performed to remove those portions ofthe sheet of material that are not protected by the remainingphotoresist. The remaining photoresist is then removed leaving theheating element 150 shown in FIGS. 6 and 7. In certain examples, thesheet of conductive material is etched from both sides simultaneouslydue to the sheet of material not being attached to a substrate duringthe photolithography process.

The photolithography process optimizes the structure of the heatingelement 150 by imparting a continuous and smooth transition between theterminals 130, heating element segments 134, and buses 136 which are allpart of the same continuous sheet of material. This improves the currentflow through the heating element 150, and accordingly, improves theperformance of the heating element 150 so that the infrared radiationgenerated by heating element 150 reaches higher temperatures in lesstime.

In another possible example, other techniques such as machining and/orpunching are done to process the blank sheet of material to form theterminals 130, heating element segments 134, and buses 136 as acontinuous single sheet of material. For example, machining or cuttingcan be performed by a computer numerical control (CNC) router or similarmachine.

By forming the terminals 130, heating element segments 134, and buses136 all from a single sheet of material, the heating element 150 doesnot have any joints where two separate pieces of metal need to befastened together. This is advantageous for several reasons. One benefitis that joints in a heating element are a potential source of failurebecause the joint can oxidize over time with the exposure to electricityand oxygen. Oxidation reduces the conductivity at that point, reducingthe amount of current that can flow and creating a cold spot.Eliminating the joints therefore improves the operation and reduces thechance of undesirable oxidation occurring in the heating element 150.Another benefit is that the components (terminals, heating elementsegments, and buses) are all connected together to begin with, andtherefore no manufacturing steps are required in order to connect thesecomponents together.

After the blank sheet of conductive material has been processed, thefinished heating element 150 may have a thickness T1 (depicted in FIG.7). The thickness T1 can be selected for the heating element 150 to havea desired power output, current flow, and resistance. In certainexamples, the thickness T1 is in a range from about ⅛ mm to about ⅜ mm,or about ¼ mm. In certain examples, the dimensions and material of thefinished heating element 150 enable the heating element 150 to receiveabout 55V and to produce about 350 W+/−10% of energy.

The various embodiments described above are provided by way ofillustration only and should not be construed to limit the claimsattached hereto. Those skilled in the art will readily recognize variousmodifications and changes that may be made without following the exampleembodiments and applications illustrated and described herein, andwithout departing from the true spirit and scope of the followingclaims.

What is claimed is:
 1. A heating element for a cooking appliance, theheating element comprising: a plurality of heating element segments,each heating element segment extending between first and second terminalends and defining a sheet having a plurality of cutouts and first andsecond opposed sides; and a reflector located adjacent the second sideof the plurality of heating element segments, the plurality of heatingelement segments being mechanically supported to the reflector byelectrically insulated mechanical supports that allow the heatingelement segments to thermally expand and contract; wherein the pluralityof heating element segments are electrically connected together inseries and have their respective first sides exposed for emittinginfrared radiation toward a cooking cavity of the cooking appliance. 2.The heating element of claim 1, further comprising one or more busesarranged between the first and second terminal ends of adjacent heatingelement segments, the one or more buses connecting the plurality ofheating element segments in a zig-zag configuration.
 3. A heatingelement for a cooking appliance, the heating element comprising: aplurality of heating element segments, each heating element segmentextending between first and second terminal ends and defining a sheethaving a plurality of cutouts and first and second opposed sides;wherein the plurality of heating element segments are electricallyconnected together in series and have their respective first sidesexposed for emitting infrared radiation toward a cooking cavity of thecooking appliance; wherein the plurality of heating element segmentsincludes a first set of heating element segments having a first length,a second set of heating element segments having a second length, and athird set of heating element segments having a third length; and whereinthe third set of heating element segments are arranged between the firstand second sets of heating element segments, and wherein the firstlength is less than the second length, and the second length is lessthan the third length.
 4. The heating element of claim 3, wherein thelength of the first set of heating element segments is about 70% toabout 90% the length of the third set of heating element segments, andwherein the length of the second set of heating element segments isabout 80% to about 99% the length of the third set of heating elementsegments.
 5. The heating element of claim 3, wherein the first length,second length, and third length define an optimized heating surface areathat reduces energy waste.
 6. The heating element of claim 1, whereinthe sheet defined by each of the plurality of heating element segmentshas a length and a width where the length is larger than the width, andwherein the plurality of heating element segments are arranged parallelto each other with the length of each of the plurality of heatingelement segments extending in a same direction.
 7. The heating elementof claim 1, wherein each heating element segment has a width, andwherein the heating element has a total width greater than a sum of thewidths of the-plurality of-heating element segments.
 8. The heatingelement of claim 7, wherein the total width of the heating element isabout 35% to about 45% greater than the sum of the widths of theplurality of heating element segments.
 9. The heating element of claim1, wherein each cutout is defined by first and second walls that arecurved and that flare out in opposing directions along a vertical axis.10. The heating element of claim 9, wherein each cutout is adjacent tothe opposing first or second wall of an adjacent cutout.
 11. The heatingelement of claim 1, wherein the heating element generates the infraredradiation when an AC voltage is applied across the heating element. 12.A toaster comprising the heating element of claim
 1. 13. The heatingelement of claim 1, wherein the reflector is arranged to reflect theinfrared radiation emitted by the plurality of heating element segmentstoward the plurality of heating element segments.
 14. The heatingelement of claim 1, wherein the reflector is electrically and thermallyinsulating.
 15. The heating element of claim 1, wherein each of theplurality of heating element segments is attached to the reflector atthe respective first and second terminal ends.
 16. The heating elementof claim 1, wherein the reflector is defined by a sheet of material. 17.The heating element of claim 1, wherein terminal ends of adjacentheating element segments are electrically and mechanically connected bya bus.
 18. A heating element for a cooking appliance, the heatingelement comprising: a plurality of heating element segments, eachheating element segment extending between first and second terminal endsand defining a sheet having a plurality of cutouts and first and secondopposed sides, wherein terminal ends of adjacent heating elementsegments are electrically and mechanically connected by a bus; and areflector located adjacent the second side of the plurality of heatingelement segments, the plurality of heating element segments beingattached to the reflector by a fastener engaged with an opening in arespective bus; wherein the plurality of heating element segments areelectrically connected together in series and have their respectivefirst sides exposed for emitting infrared radiation toward a cookingcavity of the cooking appliance.
 19. The heating element of claim 1,wherein the sheet defined by each of the plurality of heating elementsegments has a length and a width where the length is larger than thewidth, and wherein the plurality of heating element segments arearranged parallel to each other with the length of each of the pluralityof heating element segments extending in a vertical direction.
 20. Acooking appliance comprising: a housing defining a cooking cavity forreceiving food therein; an electrical power cable including electricalconductors, configured for connection to a mains power source; and aheating assembly arranged to provide infrared radiation into the cookingcavity, the heating assembly being electrically connected to theelectrical power cable, the heating assembly including at least oneheating element that includes: a plurality of heating element segments,each heating element segment extending between first and second terminalends and defining a sheet having a plurality of cutouts and first andsecond opposed sides; and a reflector supporting the plurality ofheating element segments, the second side of the plurality of heatingelement segments being adjacent the reflector; wherein the plurality ofheating element segments are electrically connected together in seriesand have their respective first sides exposed to the cooking cavity toemit infrared radiation toward the cooking cavity, and wherein theplurality of heating element segments are mechanically supported to thereflector by electrically insulated mechanical supports that allow theheating element segments to thermally expand and contract.
 21. Thecooking appliance of claim 20, wherein the heating assembly furtherincludes one or more buses arranged between the first and secondterminal ends of adjacent heating element segments, the one or morebuses connecting the plurality of heating element segments in a zig-zagconfiguration.
 22. The cooking appliance of claim 20, wherein theheating assembly further includes a first set of heating elementsegments having a first length, a second set of heating element segmentshaving a second length, and a third set of heating element segmentshaving a third length; wherein the third set of heating element segmentsare arranged between the first and second sets of heating elementsegments, and wherein first length is less than the second length, andthe second length is less than the third length.
 23. The cookingappliance of claim 22, wherein the first length, second length, andthird length define an optimized heating surface area that reducesenergy waste by limiting heat from being applied to spaces in thecooking cavity that are not proximate to food.
 24. The cooking applianceof claim 20, wherein each cutout is defined by first and second wallsthat are curved and that flare out in opposing directions along avertical axis.
 25. The cooking appliance of claim 20, wherein thecooking appliance is a toaster having parallel cooking cavities; and thecooking appliance further comprises the heating assemblies mountedadjacent to opposing sides in each cooking cavity.
 26. The cookingappliance of claim 20, wherein the heating assembly generates theinfrared radiation when an AC voltage is applied across the heatingelement segments.
 27. The cooking appliance of claim 20, wherein thereflector is arranged to reflect infrared radiation emitted by theplurality of heating element segments toward the cooking cavity.
 28. Thecooking appliance of claim 20, wherein the reflector is electrically andthermally insulating.
 29. The cooking appliance of claim 20, whereineach of the plurality of heating element segments is attached to thereflector at the respective first and second terminal ends.
 30. Thecooking appliance of claim 20, wherein the reflector is defined by asheet of material.
 31. The cooking appliance of claim 20, wherein theterminal ends of adjacent heating element segments are electrically andmechanically connected by a bus.
 32. A cooking appliance comprising: ahousing defining a cooking cavity for receiving food therein; anelectrical power cable including electrical conductors, configured forconnection to a mains power source; and a heating assembly arranged toprovide infrared radiation into the cooking cavity, the heating assemblybeing electrically connected to the electrical power cable, the heatingassembly including at least one heating element that includes: aplurality of heating element segments, each heating element segmentextending between first and second terminal ends and defining a sheethaving a plurality of cutouts and first and second opposed sides; and areflector supporting the plurality of heating element segments, thesecond side of the plurality of heating element segments being adjacentthe reflector; wherein the plurality of heating element segments areelectrically connected together in series and have their respectivefirst sides exposed to the cooking cavity to emit infrared radiationtoward the cooking cavity, wherein the heating element segments areattached to the reflector by a fastener engaged with an opening in arespective bus.
 33. The cooking appliance of claim 20, wherein the sheetdefined by each of the plurality of heating element segments has alength and a width where the length is larger than the width, andwherein the plurality of heating element segments are arranged parallelto each other with the length of each of the plurality of heatingelement segments extending in a vertical direction.